Snowshoes need to be able to hold up weight and resist water among other things. That makes stainless steel the best material for the frame of the snowshoes. Snowshoes can encounter rocks and other hard objects so that is another reason for stainless steel. Snowshoes made with aluminum will be good but with stainless steel even better.
A snowshoe is made of several different types of materials. The best and most commonly used material in a snowshoe is aluminum for the frames and nylon for the decking.